In recent years, the oil and gas exploration and production industry has made increasing use of expandable tubing for use as bore-lining casing and liner, in straddles, and as a support for expandable sand screens. Various forms of expansion tools have been utilised, earlier proposals including expansion dies, cones and mandrels which are pushed or pulled through tubing by mechanical or hydraulic forces. More recently, rotary expansion tools have been employed, these tools featuring rolling elements for rolling contact with the tubing to be expanded while the tool is rotated and advanced through the tubing. Each of these expansion apparatus offers different advantages, however there is a limit to the degree of expansion that is achievable using such expansion tools.
When an expandable tubular is run into a wellbore, it must be anchored within the wellbore at the desired depth to prevent rotation of the expandable tubular during the expansion process. Anchoring the expandable tubular within the wellbore allows expansion of the length of the expandable tubular into the wellbore by an expander tool. The anchor must provide adequate frictional engagement between the expandable tubular and the inner diameter of the wellbore to stabilize the expandable tubular against rotational and longitudinal axial movement within the wellbore during the expansion process.
The expandable tubular used to isolate the area of interest is often run into the wellbore after previous strings of casing are already set within the wellbore. The expandable tubular for isolating an area of interest must be run through the inner diameter of the previous strings of casing to reach the portion of the open hole wellbore slated for isolation, which is located below the previously set strings of casing. Accordingly, the outer diameter of the anchor and the expandable tubular must be smaller than all previous casing strings lining the wellbore in order to run through the liner to the depth at which the open hole wellbore exists.
Additionally, once the expandable tubular reaches the open hole portion of the wellbore below the casing liner, the inner diameter of the open hole portion of the wellbore is often larger than the inner diameter of the casing liner. To hold the expandable tubular in place within the open hole portion of the wellbore before initiating the expansion process, the expanded anchor must have a large enough outer diameter to sufficiently fix the expandable tubular at a position within the open hole wellbore before the expansion process begins.
It is among the objectives of embodiments of the present invention to provide a method of expanding tubing downhole which permits a relatively large degree of expansion to be achieved. It is also among the objectives of embodiments of the present invention to provide an anchor to support an expandable tubular used to isolate an area of interest within a wellbore prior to initiating and during the expansion of the expandable tubular. There is a need for an anchor which is small enough to run through the previous casing liner in the wellbore, capable of expanding to a large enough diameter to frictionally engage the inner diameter of the open hole wellbore below the casing liner, and capable of holding the expandable tubular in position axially and rotationally during the expansion of the length of the expandable tubular.